The Unknown Unknowns of Global Warming

Plants, both through decay and respiration, are responsible for over half of the world’s annual carbon dioxide emissions.

I mention this fact for one reason and that is to communicate the power of the biosphere upon the atmosphere.

Usually, when discussed in the context of climate change, we talk about the opposite phenomenon, which is the power of the atmosphere on the biosphere. Specifically, the increased growth rate of plants in response to increased levels of atmospheric carbon dioxide.

But that focus on the biological benefits of carbon dioxide has limited our view. How does the biosphere affect the climate? Or, to be more precise, how does the changing biosphere, in response to carbon dioxide emissions, affect the climate?

I would like to propose a new climate feedback for the IPCC. Unfortunately for their organization this is a negative climate feedback. My proposition is a simple one based on these facts:

2) With less stomata open plants will lose less water due to transpiration

3) This means less water vapor in the atmosphere – less of a powerful greenhouse gas (WUWT?).

Simply put, higher levels of carbon dioxide, all other things being equal (which we know they aren’t), will decrease levels of water vapor in the atmosphere and therefore the greenhouse effect. This effect will obviously be shown above land rather than the oceans, but then again, the atmosphere above the oceans is already very humid, far overpowering carbon dioxide.

Is this a powerful effect? I don’t know. But keep in mind the first sentence in this article before dismissing its magnitude out of hand. It is certainly something I’d like to see tested under strictly controlled conditions.

The effect would probably be logarithmic in nature, just like the radiative forcing of carbon dioxide is logarithmic, because plants can only grow and store so much water in the limited amount of real estate we have. However, plants do have another interesting, but somewhat predictable response to carbon dioxide – they increase the size of their root systems.

Since their leaves are more capable of supplying the needed carbon the limiting factor for growth becomes the minerals extracted by their roots.

Solution: Grow more and deeper roots.

That is one way the extra water might be stored.

Of course, in his book, A Many-Colored Glass, Freeman Dyson discusses the effects of these more intricate root systems. He postulates that as plants grow more roots and less shoots that their ultimate decay will return more of the carbon to the soil and less to the atmosphere.

That could certainly throw a damper on their multi-century long predictions of atmospheric carbon dioxide levels, especially, and again I defer to Dyson,when he calculates that half of the landmass on Earth would only have increase in thickness by 1/100th of an inch per year in order to absorb every last drop of our carbon dioxide emissions.

Conclusion:

This example was meant to demonstrate how little we know about the climate and, more importantly, the things we didn’t even realize we didn’t know. How many more mysteries are out there befuddling climate models and their predictions?

As simple as this example is, it is still far more complex than the calculations regarding carbon dioxide.

Or is it?

When clouds precipitate away their moisture, releasing heat towards both Heaven and Earth, wouldn’t the carbon dioxide reflect some of that heat back up towards space? Or would those conditions necessarily require a high amount of water vapor in the air which would drown out that effect?

I don’t know. Maybe it is a stupid question – or perhaps just another unknown unknown.

60 thoughts on “The Unknown Unknowns of Global Warming”

Yet another in the growing list of questions the Warmistas must,
perforce, assiduously ignore.
In fact, they’re out of fundamental questions
because they already know the Answer:
Satanic Gases be gone!

Evapotranspiration accounts for about 10% of water vapour entering the atmosphere (see link). 90% comes from direct evaporation from land and water bodies. So, even if it were true that evapotranspiration decreases due to increased CO2, that effect would have to overcome increased evaporation due to higher temperature. And as 90% of water vapour comes from evaporation, that’s a lot to overcome. And evapotranspiration also increases due to higher temperature. So, even ignoring evaporation, if both temperature and CO2 rise, the direct effect of temperature will counteract the indirect effect of CO2 on evapotranspiration.

Before saying “more research is needed”, you should look to see if it has already been done. My guess is that it is already well known among experts that this effect is insignificant. I am ready to be proven wrong on that.

And of course increased plant growth means more photosynthesis and therefore energy absorption from the radiation budget…

[Note – RW – there has been another commenter using this handle here occasionally over the past year whose behaviour and contentious comments resulted in warnings from Anthony. Just warning you to be prepared to politely deflect any replies that may be the result of this person’s reputation or perhaps be prepared to change your handle ~jove, mod]

I have a lot of respect for Dyson but even if I’d never heard of him, your question makes sense. I hope we can hear from plant experts or people who know whether/how the experiments have been done or could/should be done. There is plenty of data showing how plants thrive with more CO2, but how that translates to demonstrations outside a greenhouse with complex ecosystems over time, I don’t know. I do know that the AGW camp are unlikely to volunteer to fund the research…

In a recent GCM study, tropical photosynthesis and transpiration rates were calculated to change only slightly under a CO2 concentration of 700 ppm, while the additional surface net radiation due to global warming was mainly returned to the atmosphere as sensible heat flux, boosting warming over the tropical continents by 0.4 to 0.9°C above the direct greenhouse warming of 1.7°C (Sellers et al., 1996a). It has been hypothesised that this effect may be partially countered by increased vegetation growth (Betts et al., 1997), but it is not clear to what extent this would be significant in already densely vegetated areas such as the tropical forests. To what extent can we trust these new models and their predictions?

What makes you think that decreased transpiration has to “overcome” the 90% of vapour from other sources? Water vapour causes somewhere up to 95% of the greenhouse effect. Our own activities account for between about 0.3 and 1%. So it is entirely possible that a reduction in evapotranspiration of about 3% would wipe out all human influence on the greenhouse effect.

Since palaeo-stomata studies suggest fairly large variations in response to carbon dioxide levels, this is far from unlikely, and could easily overcome the increase in evaporation from the very small temperature increases some parts of the world are seeing.

Under what conditions? Were the plants grown for several generations under increased carbon-dioxide concentrations? What plant types were studied, all of them? Did they increase the range of the plants that responded most to carbon dioxide, at the expense of those that responded least? Did they assume an increased range for all plants that grow better with higher carbon dioxide (at the moment we are in a carbon dioxide crisis, with very low levels compared to earlier periods in the Earth’s history; this has been detrimental to some classes of plants)?

Such studies are often (of necessity) far too restricted to say much of any use about the real world.

Another limiting factor for plant growth: Warmth. An experiment was done that found that leaves maintain a fairly consistent temperature inside their leaves as they grow. I think it was around 21 C, and this was only for one type of plant. Other plants might have different optimal internal temperatures, but what about those that prefer 21C? As the lower troposphere warms from the average 14C, then plants won’t have to work so hard to bring their leaf internal temperatures up to 21C. Warmer temperatures could promote more growth if warmth was a bottle neck or ‘lowest plank in the barrel’ that limited growth.

I love the idea of more roots in a CO2 enriched growing environment because of lack of minerals in the growing medium. That lays question to the claim that daffodils, for example, from certain companies are better simply because they have larger root systems.

From what I have read Plants are CO2 neutral. ie All the CO2 that plants can use is absorbed through photosynthesis . High CO2 levels increases growth but eventually all plants die and the CO2 is released in to atmosphere. No net change.

The important item is timing. Low CO2 level means stunted growth and I suspect shorter life spans. High CO2 leads to a greater quantity of foliage , increased life spans of plants and a greater turn over of water ( transpiration) . Leading to a higher humidity, increased rain and in turn greater plant growth.

The age of the Dinosaurs – higher CO2 levels – higher temps – higher rainfall. The greatest quantity and most diverse amount of life on this planet.

Be nice to have those conditions back again.

Instead we are looking at an Ice Age. Real Deal.

The greatest moderator of CO2 is the Ocean. As temps fall water absorbs CO2.

As water temps increase CO2 is released. This has the effect of increasing plant growth

As water temps decrease CO2 is absorbed. Ocean temps and levels are decreasing.

That can only mean 2 things.

1 – Ocean levels go down – Ice quantity in the world is going up. ( where is the water going)

Most important climate change factor and ‘known unknown’ is the sun’s input, but not the usually considered TSI, cosmic rays, UV, etc.http://www.vukcevic.talktalk.net/CDr.htm
the rest are minor factors or indirect consequences.

What makes you think that decreased transpiration has to “overcome” the 90% of vapour from other sources? Water vapour causes somewhere up to 95% of the greenhouse effect. Our own activities between about 0.3 and 1%. So it is entirely possible that a reduction in evapotranspiration of about 3% would wipe out all human influence on the greenhouse effect.

Since palaeo-stomata studies suggest fairly large variations in response to carbon dioxide levels, this is far from unlikely, and could easily overcome the increase in evaporation from the very small temperature increases some parts of the world are seeing.

————–

I fear you misunderstood me. 90% of water vapour comes from evaporation, Only 10% from transpiration. If temperature and CO2 rise, the predominant effect will be inreased water vapour from evaporation. That effect is what decreased transpiration, if it occurred at all, would have to overcome if the net effect were to be decreased water vapour.

And bluegrue is suggesting that it is already known that transpiration rates do not change significantly due to CO2 concentrations of up to 700ppm.

Paul Cantwell says:
October 29, 2011 at 5:01 am
From what I have read Plants are CO2 neutral. ie All the CO2 that plants can use is absorbed through photosynthesis . High CO2 levels increases growth but eventually all plants die and the CO2 is released in to atmosphere. No net change.
—————-
The carbon may eventually be released in the atmosphere, but it can take a long time. Fossil fuels are an example of carbon that was once in the atmosphere. As long as there as an increase in plant matter, the CO2 sink is larger..

When faced with more CO2 in the atmosphere, plants have 3 “options”

1. Keep capturing the same amount of CO2 as before, which means they won’t need to keep their stomata open as long –> less evaporation.

2. Keep their stomata open as long as before, which means they will absorbe more CO2 — > more plant growth.

3. A combination of the above.

The most common option is 3, by far. So there is both more plant growth and less evaporation.

More plants means a bigger CO2 sink.

Plants also release other chemicals that have a cooling effect.
See for example:http://www.co2science.org/about/position/globalwarming.php
“Carbon dioxide is a powerful aerial fertilizer, directly enhancing the growth of almost all terrestrial plants and many aquatic plants as its atmospheric concentration rises. And just as increased algal productivity at sea increases the emission of sulfur gases to the atmosphere, ultimately leading to more and brighter clouds over the world’s oceans, so too do CO2-induced increases in terrestrial plant productivity lead to enhanced emissions of various sulfur gases over land, where they likewise ultimately cool the planet. In addition, many non-sulfur-based biogenic materials of the terrestrial environment play major roles as water- and ice-nucleating aerosols; and the airborne presence of these materials should also be enhanced by rising levels of atmospheric CO2. Hence, it is possible that incorporation of this multifaceted CO2-induced cooling effect into the suite of equations that comprise the current generation of global climate models might actually tip the climatic scales in favor of global cooling in the face of continued growth of anthropogenic CO2 emissions.”

The balance of water vapor in the atmosphere does not directly depend on the amount of evaporation. The capacity of the atmosphere to hold water vapor depends on the temperature, but the removal of water vapor from the atmosphere (rain) also depends on the relative humidity. If there is less rain, the replacement vapor due to evaporation does not have to be as large to maintain or even increase the absolute vapor content. Supporters of the CAGW hypothesis and many modelers assumed constant relative humidity, and thus increasing absolute water vapor content with increasing temperature. However, data shows not only dropping relative humidity with increasing temperature, but even dropping to near constant absolute water vapor levels at higher altitudes, which is the opposite of what is needed for positive feedback.

The point I am making here is that the evaporation level is not the only factor for amount of vapor in the atmosphere, so your point is moot.

a)1) As carbon dioxide levels increase plants need to keep less stomata (pores) open to absorb adequate levels of carbon dioxide
I have to admit, I don’t know much about plants in this specific case. But that sounds quite illogical to me, because plants grow better at higher CO2 conditions and I can’t see, how that correlates with lesser stomata. This would rather mean a growth stagnation, which isn’t.

b)3) This means less water vapor in the atmosphere – less of a powerful greenhouse gas
Water vapor level only changed insignificantly over the decades, and as John B. already adumbrated, water vapor seems to come mostly from ocean and land evaporation.
[Although I have to admit, that my room plants are very thirsty and need lots of water :-) ]

As for me, a very good explanation for interaction of water vapor an CO2 in the atmosphere maintaining a constant optical depth, is shown in the paper from Miskolczi:

“There are known knowns; there are things we know we know.
We also know there are known unknowns; that is to say we know there are some things we do not know.
But there are also unknown unknowns – the ones we don’t know we don’t know. ”
—Former United States Secretary of Defense Donald Rumsfeld

1.The role of the thermohaline circulatory patterns on climate.
2.The cyclical nature of key emissions of the sun, notably CMEs and X-rated flares.
3. The amount of reafforestation, its type, its location and the rate of subsequent growth which humans, in their infinite wisdom, will allow to take place in the next 500 years.
4. The effect of a 30 year shift in the jet stream further south over the Atlantic, in particular its effect on desert- or semi-desert areas of N. Africa and Southern Europe,in terms of the levels of water in aquifers, the spread of vegetation within the deserts and changes in climate and local temperature which may or may not accrue as a result.
5. What the stable human population will end up being: 10 billion, 15 billion or 25 billion plus?
6. How effectively the oceans transfer heat from the surface layer to deeper levels, since Sea Surface Temperature is but a minor measure of the overall oceanic temperature index…..
7. How evolving levels of atmospheric pollutants will affect the atmospheric energy budget.

c3 plants fix three carbon atoms during photosynthesis, c4 fix four. Most plants are c3 but we are presently growing more c4 plants commercially, thanks to maize. Additionally, we are bio-enineering c3 plants with c4 genes to make them more water efficient. Furthermore we are growing more maize and other oddities to produce ethanol. I doubt that all the co2 is released into the atmosphere when a plant dies, rather more will be “adsorbed” and remain in the topsoil.

I think there are plans to make rice a c4 plant, that could be interesting.

Cactus do not photosynthesize in real-time like c3 and c4 plants, rather, they store up what they need to perform a type of photosynthesis later, in low light or night.

bluegrue says:
October 29, 2011 at 4:04 am
In a recent GCM study, tropical photosynthesis and transpiration rates were calculated to change only slightly under a CO2 concentration of 700 ppm
==========================================================
..a recent study…GCM…calculated… Sigh!.
What do real experiments (plural) show when plants are grow in higher C02 environments?

To add a couple of more unknows that complicate the models, what are the mean residence times of carbon in the life cycles in the biosphere? Think about decaying leaf litter, phytoplankton, swamp gas, and methane hydrates. The actual residence time of CO2 in the atmosphere as a gas is probably a matter of days, but the “observed” environmental residence time depends on these cycles with the atmosphere.

“jmrSudbury
An experiment was done that found that leaves maintain a fairly consistent temperature inside their leaves as they grow. I think it was around 21 C, and this was only for one type of plant. Other plants might have different optimal internal temperatures, but what about those that prefer 21C? ”

Living organisms do have an ‘optimal internal temperature’, but not for the reason you think. There is a relationship between the rate a particular enzyme turns over and temperature, however, this is ‘tunable’ in evolutionary time; it would be very easy to tune all the biochemistry to 11 degrees or to 31 degrees. Enteric bacteria spend time inside intestines at 37 and then when pooped out, at ambient temperature; their biochemistry is tuned to be dynamic.
The operating temperature of a plant or animal is actually, surprise surprise, a compromize.
Plants and animals can generate heat by thermogenesis, which requires energy, and cool themselves by transpiration/panting/sweating, which also requires energy and resources.
The ‘optimal internal temperature’ of a particular species, sometimes the same species in a different location, represents the lowest energy cost required to buffer internal temperature using heating/cooling energy consuming processes.
The smaller you are, the less the payoff in the attempt. Bacteria quite simply don’t bother with this game and instead of buffering their temperature, they buffer their biochemistry. The bigger you are, the bigger the payoff. Having a constant internal temperature means that signaling pathways become increasingly refined, it is easier for cell to measure what is going on in different pathways and easier to fine tune them. Mammals are pretty much the masters of this, by removing (thermal) noise from their biochemistry, they can read/write information wonderfully.
Different mammals have different optima. The bigger you are there less your body temperature swings during the day/night cycle. Mammals also split themselves into two, a core body where all the important stuff happens (the organs) and the non-core extremities. Through the regulation of blood flow the core temperature is maintained and skin, for example, goes on a roller coaster ride.
There is a nice dog core body plot somewhere that shows the average rectal temperature of dog breeds vs. body mass. Large dogs have a lower working temperature than small dogs. It is easier for large to dog generate heat than to lose heat, so they sit on the left hand side of the curve, whereas with small dogs it is the opposite.

from John B
“Evapotranspiration accounts for about 10% of water vapour entering the atmosphere (see link). 90% comes from direct evaporation from land and water bodies.”

But increasing the leafy mass also shades the ground and thereby reduces the direct evaporation as well. There are researchers in the Midwest USA that suspect that the increasing planting density of corn the last 20 years has resulted in moderating the high temperatures.

This is why WUWT is the best science website on the Internet. John B is allowed to make intelligent comments without edition. He makes excellent points that we must all consider. True, some here are a bit rude in their criticisms but at least John B has the courage and intellect to post a thought provoking comment. When you are surrounding by yes-men as we see at Real Climate, no progress can be made toward the truth of climate variability.
I am not convinced that CAGW will doom the planet but I am thankful that thoughtful criticisms are always allowed at WUWT. For me it is the highlight of the day to click on WUWT in my favorites list and enjoy the mental stimulation of a spirited climate debate based on solid thinking. But I do wish we could all be a bit more diplomatic in our expressions. The art of the skilled wordsmith is too often absent in the climate debate. Perhaps I am a throw back to a bygone era but I prefer a more stately tone and a modicum of gentlemanly conduct.
The idea that the atmosphere and the biosphere always try to reach an equilibrium state in a giant reversible reaction must of course be true. It is a wildly complex relationship that is beyond both belief and description, it seems. The suggestion by Padgett that we ought to consider putting renewed interest in studying the reaction from the opposite direction is refreshing. In order to illustrate this he has selected the idea of how water is transported back and forth from plants to air. The resulting equilibrium state (if there is one) will oscillate according to CO2, temperature and water vapour content. Predicting the magnitude of the effect on long term climate change is conjecture at this point but the idea that plant growth, plant biological response and its combined effect on climate is more than intriguing. One might consider the biological response as a kind of buffering effect on any run away green house effect. Paul Cantwell’s comment regarding mega tropical conditions during the age of the Dinosaurs and I suppose more recently the rise of the Mega Fauna as the glaciers retreated must also indicate how a massive biological response may both drive and be controlled by climate.
I like the concept that Padgett has reminded us of. Atmospheric and Biospheric equilibrium reactions are worthy of intense study even if the water exchange argument is not the whole story.

This is the philosophical divide between the two camps.
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Exactly! Based on what we think we know historically, the earth spends way too much time in ice ages with occasional warm interludes. We are in a warm interlude which is very favorable to plants and animals. If there is any tipping point to worry about it is one that would have us going back into an ice age. It is all in your perspective. I think some people (the alarmists) just can’t stand prosperity.

This post has simailarities with the website http://www.bioticregulation.ru/index.php
You will find some interesting publications there but please note while most of the publications are peer reviewed that does not mean they are perfect or open to debate. Dr Anastassia Makarieva has had problems with getting a paper on condensation published in some journals.

Sorry if I can’t respond to everyone, but I’ll try to clarify some things up a bit.

@JohnB Yes, I realize that direct evaporation is far more significant, but I also realize that natural sources of carbon dioxide greatly exceed any carbon dioxide emissions from man. As with CO2, this would effect would not be limited to a single year and so you’d have to consider the cumulative effect of increased plant growth and their increased storage of water.

You must also keep in mind where the vast majority of direct evaporation is occurring. I thought I made this clear in my post that it was over the oceans. This reduced humidity would be over the land, which increases its likelihood of having a climatic effect.

@BlueGrue To my knowledge the idea that increased carbon dioxide can have a cooling effect via the changes it induces in the biosphere is novel. I could of course be incorrect. As for the model you posted from the IPCC, keep in mind that it was predicting the response in tropical areas, which doesn’t necessarily translate into more moderate and less humid environments.

Any effect this would have on climate would be most noticeable in areas that do not maintain such high humidity levels like over the oceans or the tropics. This is quite similar to how carbon dioxide does not strongly impact these areas.

@Thomas Thank you for that, that was very interesting and lends support to my hypothesis. The critical difference is that while they understand that carbon dioxide will reduce the levels of water vapor in the atmosphere, they do not make the connection that it is reducing a greenhouse gas. Instead they seem to worry that this would reduce rainfall or cause plants to overheat.

@petermue 1) Plants do not want to keep open as many stomata as they possibly can because they will lose water in the process. They need to get the carbon that they need without losing too much of the water they need. It is a balancing act that they must maintain to stay alive and increased carbon dioxide simply gives them a pole to help keep that balance better.

2) I agree that it is difficult to tell how much of an effect this will have on the atmosphere, because, while this would decrease water vapor levels, other effects, like increased temperatures may overpower and cloud that effect.

That being said, look at my “WUWT” link in the article, where they hypothesize that the lack of warming in the last decade is linked to a 10% decrease in water vapor over that time frame. I’m not saying or even thinking there is a connection; I’m just participating in a conversation.

Of course, in his book, A Many-Colored Glass, Freeman Dyson discusses the effects of these more intricate root systems. He postulates that as plants grow more roots and less shoots that their ultimate decay will return more of the carbon to the soil and less to the atmosphere.

That could certainly throw a damper on their multi-century long predictions of atmospheric carbon dioxide levels, especially, and again I defer to Dyson,when he calculates that half of the landmass on Earth would only have increase in thickness by 1/100th of an inch per year in order to absorb every last drop of our carbon dioxide emissions.

I think Dyson maybe under-estimating the increase in soil thickness, many of the plants considered weeds have deep-diving root systems, which bring up minerals and moisture from the subsoils to be utilized by other plants growing on the topsoil. The deep-diving roots also penetrate the hardpan for aeration and water penetration, pathways for other plants root that are less vigorous and earthworms. All of this churning of organic matter is going to fluff up the soil much more than the simple volume of the organic matter, fertility should also grow dramatically. I see a lot of positive feedbacks to the biosphere and little or no negative feedbacks.

To my knowledge the idea that increased carbon dioxide can have a cooling effect via the changes it induces in the biosphere is novel. I could of course be incorrect.

The latter seems indeed to be the case. If you were to read the section of the TAR (2001) that I linked to you will also find:

Research has shown that living plants appear to actively control stomatal widths (conductance) in response to changes in water vapour and CO2 concentration to optimise the ratio of water vapour losses to CO2 uptake, and simple, robust models of the photosynthesis-conductance system in plant leaves have been constructed based on this idea, see Figure 7.5 (Farquhar et al., 1980; Collatz et al., 1991; Sellers et al., 1992a). These models have been parametrized and verified at the leaf level, and can also be scaled up to describe vegetation canopy processes at regional scales using satellite data. These third generation LSPs [land-surface parametrizations], published in the late 1990s, thus combine consistent descriptions of the physical climate system transfer processes for energy, momentum, water and heat, with the biophysics of photosynthesis (Bonan, 1995; Sellers et al., 1996c; Dickinson et al., 1998).

So the scientists did not look specifically look for a positive or negative feedback, but as good scientists should researched plant response, modeled that response and verified it against satellite measurements. Keep in mind, this is the state of the art of 2001. If you want more up to date, the IPCC FAR would be a start. You claimed the idea of stomata changing the transpiration of plants in response to CO2 concentrations was novel and speculated this feedback could be negative and especially you “would like to propose a new climate feedback for the IPCC“, implying the effect to be novel and not covered by the IPCC. It turns out by one of the most simple of google searches that this very effect has been incorporated into the science as reported by the IPCC over a decade ago, already. But here it qualifies as an unknown unknown?

“That being said, look at my “WUWT” link in the article, where they hypothesize that the lack of warming in the last decade is linked to a 10% decrease in water vapor over that time frame. I’m not saying or even thinking there is a connection; I’m just participating in a conversation.”

I submit this question to all:
Is this decrease in water vapour due to cooler ocean sst which decreases vapour pressure and reduces evaporation?

“In a recent GCM study, tropical photosynthesis and transpiration rates were calculated to change only slightly under a CO2 concentration of 700 ppm, while the additional surface net radiation due to global warming was mainly returned to the atmosphere as sensible heat flux, boosting warming over the tropical continents by 0.4 to 0.9°C above the direct greenhouse warming of 1.7°C (Sellers et al., 1996a). It has been hypothesised that this effect may be partially countered by increased vegetation growth (Betts et al., 1997), but it is not clear to what extent this would be significant in already densely vegetated areas such as the tropical forests. To what extent can we trust these new models and their predictions?”

From your own quote above, the first descriptor and the last sentence:

“In a recent GCM study….To what extent can we trust these new models and their predictions?”

In other words, the mid-section contains statements about empirical reality which were already known to be false, should have been known to be at least questionable in TAR 2001 , and perhaps were, or have since been proven false. For example, greenhouses routinely use CO2 concentrations of 1000 ppm. to stimulate photosynthetic growth more than “only slightly”. So the quote in this regard is false, if the “only slightly” was intended by you to be part of your rebuttal to the actual post, which was not limited to the tropics.

And there has been no “tropical warming”, as claimed within the quote to have already occurred at least according to the Models, and then predicted to be “boosted” with increasing levels of CO2 concentrations, up to doubling.

Evapotranspiration accounts for about 10% of water vapour entering the atmosphere (see link). 90% comes from direct evaporation from land and water bodies. So, even if it were true that evapotranspiration decreases due to increased CO2, that effect would have to overcome increased evaporation due to higher temperature. And as 90% of water vapour comes from evaporation, that’s a lot to overcome.

I see that the link says “studies have shown”, but I don’t see any actual citations, so I am fairly safe in ignoring the statement.
Secondly, we’ve been told repeatedly that an increase of ~10% in CO2 partial pressure is responsible for ~0.5°C of warming. Given that there is around 20x as much H2O as CO2, what would a change of 2% bring about? When you consider the influence of clouds on temperature (at local and global scales) how much more important does a minuscule change in local water vapor have on temperature?

To elaborate a bit more, again, I didn’t claim that plants releasing less water vapor was novel. I thought, and again, I could be wrong, that the concept of it providing a cooling effect was novel.

The IPCC appeared to look into the former, but your links shows quite a few mistakes on their part, of which JPeden elaborated on a bit. As you said BlueGrue, “the scientists did not look specifically look for a positive or negative feedback,” which was what this post was about.

So I’m not really sure what your argument is. If you like I will admit that I’m not infallible.

However, since you are good at researching, then perhaps you can help us find the equations regarding this effect that the IPCC has included in their models. That would be most helpful.

No, I didn’t misunderstand you, what you have siad is exactly what I replied to. I fear you misunderstood me. The temperature variation due to human influence on the climate is tiny, almost certainly less than half a degree (and probably much less), and mostly affects the polar regions. At low temperatures the change in partial-pressure of water vapour with temperature is very small. Most evaporation from all sources, and indeed most evapo-transpiration, occurs in the warmer regions, which are less affected at the surface by changes in greenhouse effect. However plants there are still affected by changes in carbon dioxide levels.

As for what Bluegrue says, I know what he says. I pointed out that there is no indication that a realistic experiment can be designed to show what he claims, let alone that the experiment in question was realistic.

As my previous comment suggests, such an experiment could really only provide data to enter into a model, unless an experiment the scale of a self-sustaining ecosystem (such as was attempted in biosphere 2) had been carried out. I would be surprised if such an experiment had been carried out to test this hypothesis. The problem then is that modelling is very sensitive to the assumptions of the modeller. Even with details of the parameters I would be dubious of any claim to have modelled transpiration in the world’s total plant matter; without that this is just an assertion coming from a dishonest, self-serving body, the IPCC.

Having read a lot of posts over these arguments for a number of years I would ask only one thing.
Since no one really knows exactly what is happening at present (and much less in the even ‘near future’) please precede all comments with “I believe..” or “It’s my opinion…” (with an additional “..based on zero time spent in the field” for 99.9% of most responders :) and this way we’ll have a much healthier, albeit detached from reality, discussion overall. Meanwhile the train is still running at 100 mph towards a very visible and every instant more discernibly close brick wall! (I believe).
I have had the privilege to work in the far north for some years and the Inuit there, including the elders, and their oral tradition, have no precedent for ice not forming on some of their rivers over the winter. It plays havoc on their traditional hunting and fishing patterns. But then, who are they to know anything about weather! They’ve only been living there for a few thousand years.

re “Solution: Grow more and deeper roots.That is one way the extra water might be stored.”

Some plants with deeper root systems actually dry out wet soils, lucerne/ alfalfa being a prime example with root systems that can extend 15 metres deep.
Many trees only develop root systems deep enough to satisfy their moisture requirements, thus those trees that are in wetter soils do not develop deep root systems, the roots rather tending to extend laterally instead, and are therefore more prone to being toppled by the wind.

Another limiting factor for plant growth: Warmth. An experiment was done that found that leaves maintain a fairly consistent temperature inside their leaves as they grow. I think it was around 21 C, and this was only for one type of plant. Other plants might have different optimal internal temperatures, but what about those that prefer 21C? As the lower troposphere warms from the average 14C, then plants won’t have to work so hard to bring their leaf internal temperatures up to 21C. Warmer temperatures could promote more growth if warmth was a bottle neck or ‘lowest plank in the barrel’ that limited growth.
________________________________________
Depends on the plant.

I just over seeded my warmth loving Bermuda grass (It will go dormant as of tonight’s freeze) with Abruzzi Rye, a small grain that prefers cool temps. ( combination allows 8 to 10 months of grazing)

The rye is an annual and dies off at temps of 90F or a bove.

“…Cereal rye is grown in the cool temperate zones or at high altitudes (Bushuk, 1976). It is the most winter hardy of all small cereal grains (Miller, 1984; Stoskopf, 1985) enduring all but the most severe climates (Johnny’s Selected Seeds, 1983). Its cold tolerance exceeds that of wheat, including the most hardy winter wheat varieties (Stoskopf, 1985), and it is seldom injured by cold weather (McLeod,

In the Northeast, it can be established when seeded as late as October 1 (Schonbeck, 1988). Minimal temperatures for germinating cereal rye seed have been variously given as 3 to 5, 0.6, and 1 to 2 degrees C; optimal range has been given as 25 to 31 and 13 to 18 degrees C. According to Stoskopf (1985), for vegetative growth to occur, a minimumum temperature of 4 degrees C is required. Once well established, cereal rye can withstand temperatures as low as -35 degrees C (-31 degrees F). The structure of the rye plant enables it to capture and hold protective snow cover, which enhances winter-hardiness. Cereal rye is a long-day plant and flowering is induced by 14 hours of daylight accompanied by temperatures of 5 to 10 degrees C (Stoskopf, 1985). “ http://www.sarep.ucdavis.edu/cgi-bin/ccrop.exe/show_crop_12

proponents of AGW have to tell me: why did the lesser depression NOT reduce C02 and other greenhouse gasses? Economic activity and manufacturing declined on a global scale not seen since the 30s. The fact that we cannot correlate CO2 (methane) etc to economic activity is a big problem, because it also shows that even if AGW is true curbing this same activity won’t help at all.

“High CO2 levels increases growth but eventually all plants die and the CO2 is released in to atmosphere. No net change.”

You and others pointed out the neglected question in this statement of timing. I just wanted to point out that this is the same principle as employed in the “greenhouse” theory. There, a step change in GHG would result in more energy being retained, though the steady state energy flow in and out would equilibrate. Here, a step change in CO2 results in more carbon sequestered in living plants, though the steady state flow equilibrates.

@dwb says:
October 29, 2011 at 5:49 pm “The fact that we cannot correlate CO2 (methane) etc to economic activity is a big problem”
The reason that there is no correlation to economic activity is that the changes of CO2 due to direct emission are not measurable in comparison to natural changes. Firstly, there are seasonal changes which vary by upto 15ppm due to ocean and vegetation uptake/outgas. Then there are natural events such as volcanoes & forest fires. Then there are natural variations in SSTs. There is no reason to believe that the relatively constant 280ppm of CO2 obtained from proxy data is accurate. For their own selfish interests AGW believers have decided to discard accurate measurements with chemical instruments made by experts including Nobel prize winning chemists and biologists. Have a look at this website http://www.biomind.de/realCO2/realCO2-1.htm and open your mind to some of the complexity of atmospheric changes.

3) This means less water vapor in the atmosphere – less of a powerful greenhouse gas (WUWT?).
———–
Well Rumsfeld overlooked some important additional elements in his taxonomy:
1. The things you know and don’t want to know.
2. The things you dont know and don’t want to know,
Seems to me these additional items were the cause of some much grief in Iraq.

Any how, philosophy aside, I will point out the obvious: the amount of water vapour in the atmosphere is not dependent on just one process. It depends on the BALANCE of 2 process. Evaporation/transpiration and precipitation

If you get more evaporation/transpiration the balance is maintained by more precipitation.

So according to the suggested hypothesis more CO2 means less transpiration and therefore less rain. To get this hypothesis to work in the way suggested it would need to show that there would develop an imbalance between the two processes.

P.S. The writer assumes the IPCC has not considered this. They may or may not but this smells like an assumption.

cementafriend says:
October 29, 2011 at 6:32 pm
…. For their own selfish interests AGW believers have decided to discard accurate measurements with chemical instruments made by experts including Nobel prize winning chemists and biologists. Have a look at this website http://www.biomind.de/realCO2/realCO2-1.htm and open your mind to some of the complexity of atmospheric changes.
___________________________________

The whole CO2 record stinks like bad fish!

The biggest stink in my mind is the ASSumption that the “background” CO2 is uniform in the atmosphere.

This ASSumption allowed them to throw out all the high readings from the historical wet chemistry record and cherry pick the low records. This particular pdf looking at the dogma and politics behind the 70 years of CO2 measurement as well as the science. It is a very interesting read. http://www.co2web.info/ESEF3VO2.pdf from the website: http://www.co2web.info/

This is the part that really gets my goat.

The acknowledgement in the paper by Pales & Keeling (1965) describes how the Mauna Loa CO2 monitoring program started:

“The Scripps program to monitor CO2 in the atmosphere and oceans was conceived and initiated by Dr. Roger Revelle who was director of the Scripps Institution of Oceanography while the present work was in progress. Revelle foresaw the geochemical implications of the rise in atmospheric CO2 resulting from fossil fuel combustion, and he sought means to ensure that this ‘large scale geophysical experiment’, as he termed it, would be adequately documented as it occurred. During all stages of the present work Revelle was mentor, consultant, antagonist. He shared with us his broad knowledge of earth science and appreciation for the oceans and atmosphere as they really exist, and he inspired us to keep in sight the objectives which he had originally persuaded us to accept.”

Sounds to me more like enviromentalists looking for data to fit their pet theory.

And here is the actual a description of how they REJECT readings at Manua Loa. “4. In keeping with the requirement that CO2 in background air should be steady, we apply a general “outlier rejection” step, in which we fit a curve to the preliminary daily means for each day calculated from the hours surviving step 1 and 2, and not including times with upslope winds. All hourly averages that are further than two standard deviations, calculated for every day, away from the fitted curve (“outliers”) are rejected. This step is iterated until no more rejections occur.</b.http://www.esrl.noaa.gov/gmd/ccgg/about/co2_measurements.html

As Segalstad’s website states:

”At the Mauna Loa Observatory the measurements were taken with a new infra-red (IR) absorbing instrumental method, never validated versus the accurate wet chemical techniques. Critique has also been directed to the analytical methodology and sampling error problems (Jaworowski et al., 1992 a; and Segalstad, 1996, for further references), and the fact that the results of the measurements were “edited” (Bacastow et al., 1985); large portions of raw data were rejected, leaving just a small fraction of the raw data subjected to averaging techniques (Pales & Keeling, 1965).http://www.co2web.info/ESEF3VO2.pdf

Yes Ferdinand Engelbeen, I am well aware that Jaworowski is persona non grata for daring to criticize the Ice Core chemical analysis. However I have spent forty years tearing my hair out over the issue of the batch is “well mixed” for both solids or liquids. That was for “simple” situations with no more addition and active mixing. If there is one thing I have learned it is chemicals DO NOT mix as well as most believe. I have been FIRED for proving the erratic results were due to the poor mixing of the batch and not due to the analytical method.

That said, How the heck can ANYONE think that CO2 with multiple sinks and sources is “well mixed”???

For example:
Volcano Outgasing of CO2. “The primary source of carbon/CO2 is outgassing from the Earth’s interior at midocean ridges, hotspot volcanoes, and subduction-related volcanic arcs.”http://www.columbia.edu/~vjd1/carbon.htm

The Eyjafjallajokull eruption and its effects on Europe shows just how “well mixed” the air borne particles were and how rapidly they “mixed”

So you are talking about as much (or perhaps more ) than a 200ppm day night difference and it happens FAST as soon as air movement bring the CO2 into the area around the plant.

CO2 depletion“Plant photosynthetic activity can reduce the Co2 within the plant canopy to between 200 and 250 ppm… I observed a 50 ppm drop in within a tomato plant canopy just a few minutes after direct sunlight at dawn entered a green house (Harper et al 1979) … photosynthesis can be halted when CO2 concentration approaches 200 ppm… (Morgan 2003) Carbon dioxide is heavier than air and does not easily mix into the greenhouse atmosphere by diffusion… Source

Note the 200ppm for halting photosynthesis. I had in my early notes “200 pm CO2 trees starve” SOURCE: http://biblioteca.universia.net/ficha.do?id=912067
but the link no longer works… Now all the searches turn up papers showing 180 ppm or lower….HMMMmmmm Looks like a bit of editing so the 180 ppm in the Ice Core data doesn’t stink so bad.

I’m not sure how this impacts the hypothesis, but I believe it has been found the the root hairs in most root systems are actually in symbiotic collaboration with even more extensive (and massive?) networks of fungi, which actually do most of the heavy lifting wrt mineral extraction, water collection, etc.

look again carefully at my tables quoted above and if you really take some time to study them you can easily figure it all out for yourself:

1) first the so-called ”global warming” is not global at all.
In the Southern Hemisphere (SH) there is almost no warming. Clearly, you can see a big difference in the results for means between NH and SH? Check out these two weatherstations’ results from the antarctic.

But now, how can that be? We know from real science and experiments that the CO2 is distributed everywhere exactly the same. So, if increased CO2 were to be blamed directly due to it causing an increased greenhouse effect, should not the warming be the same everywhere in the world? So, we conclude (again) it never was the increase in GHG’s that caused any warming.

2) If you look in Argentina (where there was considerable de-forestation) you find severe cooling. If you look at Norway (where there is much increased forestry) you find warming.
3) the fact that SH has little landmass and that the NH has a lot of landmass is an another indicator that should give a clue.
4) we also know that there have been reports, e.g. from the Helsinki university that there has been increased vegetation in the past decades, especially in the NH…..

for more proof that earth is greening especially in the northern hemisphere, look here:

Some extra warming (that which some scientists have identified as being on top of that which is natural) is caused by …… more vegetation!!! Now we sit with one problem: Part of that “problem” of the extra vegetation could be caused by people wanting more trees and forests and gardens and the increase in carbon dioxide in the atmosphere acts as a fertilizer and accelerator for growth..………the circle is complete….now what?

P.S. The writer [James PadgetT] assumes the IPCC has not considered this. They may or may not but this smells like an assumption.

Whatever, Lazy, but maybe now they should ‘reconsider’ it via a “mass balance” approach?…you know, given their pristinely “scientific” drive to finally be able to get one GCM prediction right? //Not!

p.s., Lazy, you aren’t going to learn much by just sitting around sniffing yourself or by repeating memes floating around within the CO2 = CAGW Cult’s pleroma – which I assume is the same one giving you the , er, “universe” of your Iraq War “facts”.

FWIW, the Japanese satellites seem to show more CO2 / methane coming from 3rd world locations with a lot of plants. I have to wonder if “jungle rot” is more important than my car in net CO2 production. And if all those phone books in landfill sites constitute “sequestration” ;-)